This invention relates to flexible power cables in general and more particularly to profiled cores such as are used, in particular, in the design of heavy rubber cables for the mechanical stabilization of the cable.
In the mechanical design of rubber flexible cables which can be wound on drums, i.e., are forcibly guided, it is customary to strand the conductors of tbe cable about a profiled core, by means of which the conductors are fixed relative to each other in their position in space. As a result, the mechanical stability of the cable is improved. The use of a profiled core is customary especially in four conductor cables, in which the neutral conductor with its full electrical cross section forms the fourth conductor. If the cable is subjected to special tensile stresses, a support member, for instance, a steel cable can be disposed in the profiled core (DER ELEKTRIKER 11/77, page 285; "Der Elektromeister", 11/79, page 933).
The use of a profiled core is also known for power cables in which three current carrying conductors form the stranded assembly of the cable and in which further stranding elements are arranged in the corners between these conductors. In one known trailing cable, for this purpose, the neutral conductor is divided into two stranding elements, while a third stranding element is formed by two auxiliary conductors which are twisted with each other and are surrounded by a round jacket (DE-AS No. 10 28 644). In a further known mining cable, the neutral conductor is divided into thirds. The three conductors of the neutral conductor and the three current carrying conductors are twisted about a profiled core, the cross section of which has three arms and has circularly inward curved outside surfaces which correspond to the conductor. The core contains a pilot conductor in the center. Through the use of nylon yarn the pilot conductor has a certain amount of tensile strength. To increase the tensile strength of the cable as a whole, a braid of nylon threads is arranged between the inner and the outer jacket (U.S. Pat. No. 4,002,820).
For adapting heavier flexible cables to more recent developments in the field of signal transmission, it is otherwise known to arrange a stranding element which contains optical transmission elements in the outer corners of such a cable (DE-OS No. 28 01 231).
When using profiled cores which contain a steel cable as the support member of the cable, it has sometimes been found difficult, in twisting the cable core, to torsion the steel cable an amount equal to the twisting pitch of the conductors. Taking this difficulty into consideration, it is an object of the present invention, starting out from a power cable with conductors twisted about a profiled core, to design a power cable, comprising three current carrying conductors and three further stranding elements arranged in the corner spaces, in such a manner that it can be included, without difficulty, into the stranding process of the conductors and stranding elements and nevertheless ensures a secure fixation of the conductors and the stranding elements relative to each other.